Radeon RX 480 or CPU for rendering animation?
If you are using an RX480 you should get a fairly significant speed boost over your aging FX-8350.  The AMD videa cards cards have a few less supported features than Cycles than Nvidia cards on CUDA but nothing that can't be worked around.  

I'd suggest lowering the number of samples in your sampling settings and turn on the seed value being different per frame.  Video doesn't need as much refinement per frame as people think.  For the tile sizes, through experimentation I have found that larger sizes work better with GPU rendering but it is a fairly minor speed gain. 

Good luck rendering your project!